Use identity keys in CT configuration

What	Where/Who
JIRA Issue	SDK-2683
People Involved	@hborisoff

Identity keys are received with migration config and set in the CleverTap configuration. Example of JSON containing identity keys:

{
    "ct" : {
        "accountId" : "accId",
        "attributeMappings" : ...,
        "identityKeys" : ["Identity", "Phone", "Email"]
    };
    ...
}

The default value is "Identity".

If the keys are missing in the API response, or they are an empty array, they will not be updated. This means that previously saved or default keys will be used. The keys that come from the API will not be further validated and will be passed directly as-is to the CT Config.

Leanplum / Leanplum-Android-SDK

Use identity keys in CT configuration #540